Introduction to the Nikon NSR 4425i Stepper
The Nikon NSR 4425i stepper is a highly regarded model in semiconductor lithography, specifically engineered for precision processing of 6-inch wafers. Launched in 1999, the NSR 4425i reflects Nikon's dedication to optical precision and robust performance, both essential for achieving the fine nanometer-scale patterns critical in semiconductor manufacturing. Known for its stability and accuracy, the NSR 4425i remains relevant in specialized or smaller-scale production environments where consistent, high-quality patterning is required.
This article offers an in-depth look at the NSR 4425i’s technical capabilities, performance strengths, and its range of applications within semiconductor production.
Technical Specifications of the Nikon NSR 4425i
The NSR 4425i comes with an array of features geared towards precision lithography. Below is a detailed look at its core specifications:
| Feature | Details |
|---|---|
| Wafer Size | 6 inches |
| Release Year | 1999 |
| Computer System | Vax 4000/90 with DKA200, DKA300 HDDs |
| Chamber Type | ASAHI N3A-B |
| Lamp Illumination | 201.603 mW/cm², Uniformity: 1.108% |
| Alignment Sensors | LSA, FIA |
| Laser Interferometer | 5517B |
| Wafer Chuck Type | Ring (Pre2) |
| Rack Configuration | Right-side, no signal tower |
This configuration provides the NSR 4425i with the necessary stability, storage, and precision to perform reliably in various photolithography tasks.
Key System Components
Computer System
The Vax 4000/90, paired with hard drives DKA200 and DKA300, provides ample storage and computational stability for processing and recipe storage, which are vital for repeatable lithography.Chamber and Illumination System
Equipped with an ASAHI N3A-B chamber, this model’s lamp provides an average power of 201.603 mW/cm² with an impressive uniformity of 1.108%. Uniform illumination is essential in photolithography, as any variation can compromise pattern fidelity across the wafer surface.
Optical Performance and Lens Quality
The NSR 4425i’s optics are fine-tuned to achieve low distortion and high uniformity, as shown in the lens distortion and field inclination parameters:
| Optical Parameter | Specification |
|---|---|
| Lens Distortion | ±0.100 µm |
| Maximum Distortion (X, Y) | X: 0.091 µm, Y: 0.030 µm |
| Minimum Distortion (X, Y) | X: -0.046 µm, Y: -0.031 µm |
| Field Inclination Range | 1.007 µm |
| Curvature | Within -0.211 µm |
| Alignment Tolerance | UL-LR: 0.228 µm, UR-LL: 0.026 µm |
Lens Distortion Control
With lens distortion controlled within ±0.100 µm, the NSR 4425i achieves excellent pattern fidelity, ensuring transferred designs retain high alignment accuracy across the wafer. The model maintains extremely low deviation in both X and Y axes, critical for precision photolithography.
Field Inclination and Curvature Control
Field inclination is limited to 1.007 µm, while curvature falls within -0.211 µm, both of which contribute to uniform image projection. Additionally, alignment across points from upper left to lower right (UL-LR) and upper right to lower left (UR-LL) is controlled to tight tolerances, ensuring overall exposure consistency.
Reticle Management
Using a 6-inch reticle in a fixed microscope, the NSR 4425i is equipped with a 13-slot reticle library, allowing for organized and secure reticle management, reducing handling errors and minimizing potential shifts that could lead to misalignment.
Wafer Handling and Alignment Features
The NSR 4425i’s wafer handling system ensures stable and precise wafer movement, essential for accurate pattern alignment.
- Wafer Chuck Type: The ring-type chuck (Pre2) provides reliable stability during exposure.
- Loader System: Supports a flat wafer loader, enabling smooth wafer transitions, which reduces mechanical interference.
- Carrier Table and Alignment Sensors: The dual-sided carrier table (left and right) enhances workflow efficiency. Alignment sensors LSA and FIA work with a high-resolution 5517B laser interferometer to ensure precise positioning, making the NSR 4425i ideal for applications demanding strict alignment standards.
Applications and Ideal Use Cases for the Nikon NSR 4425i Stepper
The NSR 4425i excels in small-to-mid-scale production environments where 6-inch wafer processing is suitable. Below are some of its ideal applications:
Prototyping and R&D
The NSR 4425i’s precision and stability make it suitable for semiconductor prototyping, allowing researchers to create high-quality test batches with tight design parameters.MEMS and Specialty Devices
The device’s low-distortion optics and stable alignment allow it to handle the intricate designs necessary for MEMS (Micro-Electro-Mechanical Systems) and other specialty devices.Cost-Efficient Production for Legacy Technology
While newer machines may handle advanced nodes, the NSR 4425i can perform admirably in sectors not requiring the most cutting-edge technology, making it cost-effective for companies that produce legacy technology or less-complex devices.
FAQ: Common Questions About the Nikon NSR 4425i Stepper
1. What is the average power output of the NSR 4425i’s illumination system, and how uniform is it?
- Answer: The NSR 4425i's illumination system provides an average power output of 201.603 mW/cm² with a high uniformity of 1.108%. This level of uniformity is essential for consistent pattern exposure across the wafer, ensuring that each region receives a stable and even illumination.
2. What level of precision does the NSR 4425i achieve in lens distortion?
- Answer: The lens distortion of the NSR 4425i is kept within ±0.100 µm, with maximum measured distortions at X: 0.091 µm and Y: 0.030 µm. This precise control minimizes pattern deviation, making it suitable for applications that require high-fidelity patterning.
3. What types of wafers and reticles are compatible with the NSR 4425i?
- Answer: The NSR 4425i is designed for 6-inch wafers and utilizes a 6-inch fixed reticle microscope system with a 13-slot library unit for efficient reticle management. The system's versatility with standard 6-inch wafers makes it compatible with various legacy and specialty manufacturing processes.
4. Can the NSR 4425i handle high-volume production runs?
- Answer: While the NSR 4425i can support stable and precise manufacturing, it is generally best suited for small-to-mid-scale production or specialized tasks, such as prototyping, R&D, and production of MEMS and specialty devices. For high-volume production, more advanced models are typically preferred.
5. What alignment sensors are used in the NSR 4425i, and how do they contribute to accuracy?
- Answer: The NSR 4425i utilizes LSA and FIA alignment sensors, alongside a 5517B laser interferometer, to maintain precise wafer positioning. This alignment system ensures that each wafer aligns accurately during exposure, critical for maintaining consistent pattern registration and overlay accuracy across the wafer.
Conclusion: The Enduring Value of the Nikon NSR 4425i Stepper
The Nikon NSR 4425i continues to demonstrate its value in certain sectors of semiconductor manufacturing, especially where 6-inch wafer processing suffices and extreme accuracy is essential. With highly controlled lens distortion, reliable illumination uniformity, and a stable alignment system, it remains a capable choice for companies focusing on specialized or lower-volume production needs.
